Surface-alloyed metal



- Schenectady, in the county of Schenectady,'

N- FricE.

r norn 'c. KELLEY, .orfscnannnc'rni'ax, vnw YQnx. ASSIGNOR T0 coMPANY, A conro'na'rrolv OENEW YORK.

ennn mn ELECTRIC? SURFACE-ALLOYED METAL.

1; 365,499. H 0 Drawiii gi To azz whom it concern: 1

Be it known that 1,,FLOYD C. KELLEY, a citlzen of the United States, residing at State of New York, have invented certain new and useful Improvements in Surface-' Alloyed Metals, of which the following is a" A specification.

The present, invention relates to the surface treatment of metals, particularly iron, to produce an alloy with the foundation metal, and which has useful characteristics not possessed by the foundation metal, as,

for example, superior corrosion resisting properties, luster, or color.

I have discovered that when metallic chromium is brought into surface contact under suitable conditions with a foundation metal, such as iron, nickel, molybdenum, or tungsten, that the chromium enters the surface layer of the foundation metal below the melting point of either metal, and forms a layer of alloy decreasing in richness of chromium content from the surface to the interior of the foundation metal, and that the resulting alloy is resistant to corrosion and oxidation, is ductile, not excessively hard, has a bri ht shiny luster, and will take a high polish In carrying out my invention, the foundation metal, .for example, iron or steel, is heated in contact with powdered metallic chromium under non-oxidizing conditions to a temperature of about 1200 to 1350 C. Preferably the powdered metallic chromium is. admixed with a refractory, inert material,

for example, alumina or magnesia, say, in equal proportions or thereabout. Non-oxi dizing conditions may be produced by passing a current of non-oxidizing gas such as hydrogen, for example, through the receptacle, or by evacuating the receptacle. It is advantageous in some cases to add a small proportion of powdered metallic aluminum, to the'mixture to prevent oxidation of thechromium. When treating molybdenum or tungsten with chromium a temperature as high as 1500? C. may to advantage be used; in other words, the range of treating temperatures is from 1200 to 1500 C.

The duration of the treatment will vary with the penetration of alloyagc desired. When a surface layer of alloyage about 30 to 40 mils is desired the treatment-at the proper temperature is continued for about .inent. process without fusion may be termed a 06- mentation alloy to distinguish the same "from an alloy produced by fusion.

polished "and etched, shows a well-defined zone of metal adjacent thesurface in which recrystallization of the foundation metal has taken place by the penetration of the chromium into the foundation metal and alloyage therewith. Crystals extend from the outer band or zone of alloy into the unalloyed foundation metal, and in some cases grains of unalloye d foundation metal extend into the alloy band. I In some instances a well-defined band of alloy appears intermediate the outer chromium alloy and the foundation metal. The grain structure of the chromized metal is usually relatively large, the longer axis of the grains usually extend at right angles to the surface through which the chromium entered.

Chromium treated metal similarly to aluminum treated metal resists corrosion in the presence of moisture. For example, a salt spray which will rapidly corrode untreated sp aw ndeta nee. Patented Jam-11,1921. Application filed'Octobei' '23, 1919. Serial No. 33239;. I

section of the chromized metal, when iron leaves chromized iron unaltered. The

chromium treated iurface will take a high polish and has a bright luster.

The chromium treatment causes a decalbonization of the iron. The decarbonized alloy shows ferrite structure with absence of carbon. The carbon content may be restored and increased if desired by heating the treated metal in a hydrocarbon gas, or in contact with carbon. The carburized metal may be quenched in the usual manner to harden the same.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The process of providing a metal with a surface alloy of chromium which consists in heating the metal under non-oxidizing conditions in contact with a powdered charge containing metallic chromiumat a temperature of at least about 1200 C., but below the melting point of said metal.

2. The process of providing a metal with a surface alloy of chromium which consists in heating the metal under non-oxidizing conditions at a temperature of at least about 1200 C., but below the melting point of said metal, in contact with a powdered mixw 4. The recess of providing iron with a surface a1 oy'0f chromium which consists in eating the iron in hydrogen in contact with a mixture of chromium, aluminum oxid and aluminum all in; owdered form to a temperature of about l200 to l350 C.

5 As a new article of manufacture, a foundation metal having a surface layer consisting of a cementation alloy of; chro- 'ing a igh p0 mium with said foundation metal, the chlgw' I mium content ,of' said layer, decreasing to; wan the interior of said meta 'sai'dalldy havln a shiny lustei', being capable of tak-, v ish and being ies stant'qto corq rosion.

l *6. A new article of inanufactiii qi comprising an .iron article haying a surface 26 layer iron Chromium alloy produced 1: 7

cementatiom, the chromium content .(if'said layer decreasin in chromium content from the surface to the interior, sai'd alloy being resistant togorrosion.

In witness'wi' erwf, I havehereun'to w my hand this21stday of Qctober, 1919.

FLOYD o. KEL EY,

the surface of I 

